Medium-Range Atomic Correlation in Simple Liquids. III. Density Wave Theory

TL;DR

This paper introduces a novel density wave theory combining bottom-up and top-down approaches to better understand the medium-range atomic order in simple liquids and glasses, linking structure to physical properties.

Contribution

It proposes an innovative scheme that integrates local and global perspectives to explain medium-range order in liquids and glasses, advancing beyond traditional methods.

Findings

Density waves explain medium-range order in liquids.

The approach links atomic structure to viscosity and fragility.

Provides a more intuitive understanding of liquid and glass structures.

Abstract

Elucidating the atomic structure of liquid and glass is one of the important open questions in condensed matter physics. In the conventional bottom-up approach one starts with focusing on an atom and the short-range order of its neighboring atoms, and the global structure is described in terms of overlapping local clusters of atoms as building units. However, this local approach fails to explain the strong drive to form the medium-range order which is distinct in nature from the short-range order. We propose an even-handed scheme with an additional top-down approach. In the top-down approach one starts with a high-density gas state and seeks to minimize the global potential energy through density waves. The local bottom-up and global top-down driving forces are not compatible, and the competition and compromise between them result in a final structure with the medium-range order. The density waves are pinned to atoms through the phase factors and amplitudes which reflect atomic dynamics. This even-handed approach provides a more intuitive explanation of the structure of simple liquid and glass and its relation to properties of liquid, such as viscosity and fragility.